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SubjectRe: [PATCH v2] video: backlight: Remove backlight sysfs uevent
Date
On Tuesday, November 12, 2013 12:39 PM, Kyungmin Park wrote:
>
> From: Kyungmin Park <kyungmin.park@samsung.com>
>
> The most mobile phones have Ambient Light Sensors and it changes brightness according lux.
> It means it changes backlight brightness frequently by just writing sysfs node, so it generates uevent.
>
> Usually there's no user to use this backlight changes. But it forks udev worker threads and it takes
> about 5ms. The main problem is that it hurts other process activities. so remove it.
>
> Kay said
> "Uevents are for the major, low-frequent, global device state-changes,
> not for carrying-out any sort of measurement data. Subsystems which
> need that should use other facilities like poll()-able sysfs file or
> any other subscription-based, client-tracking interface which does not
> cause overhead if it isn't used. Uevents are not the right thing to
> use here, and upstream udev should not paper-over broken kernel
> subsystems."
>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

Acked-by: Jingoo Han <jg1.han@samsung.com>

Best regards,
Jingoo Han

> ---
> v1: there's still user to use BACKLIGHT_UPDATE_SYSFS. so just remove store sysfs node uevent
>
> ---
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index 94a403a..292cf99 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -172,8 +172,6 @@ static ssize_t brightness_store(struct device *dev,
> }
> mutex_unlock(&bd->ops_lock);
>
> - backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
> -
> return rc;
> }
> static DEVICE_ATTR_RW(brightness);



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